Method of refining ferrous metals

ABSTRACT

Method for refining molten metal includes the steps of adjusting the distance between a stream of molten metal and the nozzles which direct a stream of oxidizing gas against said stream to shatter it.

United States Patent Whetton May 16, 1972 I METHOD OF REFINING FERROUS R feren s Cited METALS UNITED STATES PATENTS [72] Inventor: David Arthur Whetton, Worksop, England 3,201,105 8/1965 Miller ..75/60 X 3,340,334 9/1967 Keldmann et al.. ..264/12 [73] Ass'gneei Research 2,967,351 1/1961 Roberts et al... ..264/12 x swam 2,915,380 12/1959 Hilty ...75/60 x 22 Filed; Sept. 8, 1970 2,969,282 1/1961 Churcher ..75/60 [21] App]. No.: 70,078 FOREIGN PATENTS OR APPLICATIONS Related US, Application Data 159,552 10/1964 U.S.S.R. ..75/52 256,455 9/1960 Australia..... [621 669,022 20, 1967 1,014,773 12/1965 Great Britain ..75/59 Primary ExaminerL. Dewayne Rutledge [30] Forelgn Application Prlonty Data Assistant Examiner G white Sept. 23, 1966 Great Britain ..42,550 66 Attorney-Holmium Wetherill & Brisebois 52 US. Cl. ..75/60, 75/05 c, 264/12 ABSTRACT [51] Int. Cl ..C2lc 5/00, C21c 7/00 M ethod for refinin l g mo ten metal mcludes the steps of ad ust- [58] new of Search ing the distance between a stream of molten metal and the nozzles which direct a stream of oxidizing gas against said stream to shatter it.

7 Claims, 6 Drawing Figures PATENTEHMAY m 1972 SHEEI 1 UP 3 EATENTEBMAY 16 1972 3. 663, 205

SHEET 3 OF 3 l" ,38 36 I Iw]! METHOD OF REFINING FERROUS METALS This application is a division of my prior application Ser. No. 669,022, filed Sept. 20, 1967 now U.S. Pat. No. 3,558,120.

SUMMARY OF THE INVENTION This invention is concerned with improvements in and relating to a method of refining metal.

It has been proposed to remove certain impurities from iron by oxidation of such impurities and one form of apparatus for carrying out that process comprises a tundish from which a stream of molten metal falls into a refining vessel. The freely falling stream passes gas discharge nozzles from which jets of oxidizing gas are emitted, such jets shattering the molten metal stream, the resulting particulate metal reacting with the gas and the substantially refined metal collecting in the bottom of the vessel.

The flow of metal in such apparatus will be relatively constant as between successive pours, but the degree or kind of the impurities to be removed may vary from pour to pour. For example, it may be desired to remove carbon and silicon which would require a higher oxidizing gas flow rate for a given metal flow rate than would removal of the silicon alone. Different flow rates of oxidizing gas will result in varying degrees of shatter of the metal for a given metal flow rate and hence a varying exposure of metal to the action of the gas. Additionally it is desirable to keep the molten particulate metal away from the vessel wall since the particulate metal is highly erosive.

According to the present invention there is provided apparatus for refining molten metal comprising a container for the metal, a metal discharge device, communicating with the container and a vessel below the device, to discharge a freely falling flow of metal in the vessel, and a plurality of gas discharge nozzles adjacent the path of the freely falling flow, such gas discharge nozzles being directed at the said path and being angularly adjustable to vary the angle of intersection of the jets and the path.

By means of the angular adjustment of the nozzles, the angle of intersection can be selected to provide that degree of shatter to expose an adequate surface area of the metal to the gas whether the gas flow rate and hence gas momentum is at the lower end of the scale or at the upper end when wide scatter is undesirable since this would rapidly erode the vessel. If desired the distance of the nozzles from the flow path may also be varied.

In order that the present invention may be well understood there will now be described an embodiment thereof, given by way of example only, reference being had to the accompanying drawings in which:

FIG. 1 is a diagrammatic elevation of apparatus for refining iron;

FIG. 2 is a plan view of a metal discharge device;

FIG. 3 is a side elevation of a pair of gas discharge nozzle blocks for a metal flow produced by the discharge device of FIG. 2;

FIG. 4 is a cross section of a gas discharge nozzle block;

FIG. 5 is an underneath view of gas discharge devices for shattering a cylindrical stream, and

FIG. 6 is a sectional elevation of the device on the line VI VI of FIG. 5 shown upright.

Referring to FIG. 1 the refining apparatus shown is particularly intended for refining crude iron and comprises a transfer ladle 1 having a flow control stopper 2 to control molten metal flow to a tundish 3 having a refractory outlet nozzle 4.

Beneath the tundish is a reaction vessel 5 which comprises a cover or hood portion 6, having a central aperture 7 and a gas take-off 8, and a receptacle portion 9 beneath the hood. An extractor fan 10 is located in the gas take-off, which may have a plurality of inlets symmetrically placed about the hood portion, only one being shown.

The outlet nozzle 4 may have a rectangular cross section normal to flow to provide a wide thin metal flow having a high surface to volume ratio per unit length of flow. Alternatively the nozzle cross section may be scallop edged, formed for example by a plurality of bores on centers spaced by less than the diameter of the bores, to give the same flow characteristics. In another arrangement the thin wide metal flow may be achieved by a plurality of individual cylindrical bores B set close together as shown in FIG. 2 to give a total flow which has a high surface to volume ratio.

For such forms of metal flow a gas discharge device is provided on the hood of the vessel comprising a pair of distributor blocks 12 each having one or more gas discharge nozzles to give a gas jet or jets which span substantially a wide face of the metal flow. Each block is angularly adjustable to vary the angle of intersection of the gas discharged from it with the path of metal flow.

A particular embodiment of mounting a pair of distributor blocks is shown in FIG. 4 and a cross section through one embodiment of block is shown in FIG. 3. Each block in FIG. 4 is mounted in bearings in a pair of supports 14 so as to be angularly adjustable about axis A, for which purpose a worm 16 is provided on two of the supports engaging a wormwheel 17 fast with the associated block, a drive shaft 18 being provided to 'both worms to effect simultaneous equal angular adjustment.

Additionally the supports are slidably mounted on guides 19, a support of each block including a threaded bore engaged by a suitably threaded drive shaft 20 rotation of which will adjust the spacing of the blocks. To cater for the relative movements of the supports, the drive shaft 18 is telescopic.

The block shown in FIG. 4 comprises a mild steel body 25 defining a distributor chamber 26 communicating with one face of the block by way of one or more passages 27. A suitable coupling is provided to couple the chamber to a source of oxydizing gas. The passage 27 or each passage 27, as the case may be receives an insert 28, which abuts the shoulder 30, and the shoulder 29 having a recess for seal 31. The insert is secured by means (not shown), and defines one or more ducts 32 having a convergent/divergent cross section as shown. Since the blocks will be adjacent the high temperature metal, a coolant liquid flow path 33 is provided, defined by the insert and the block. Furthermore the insert face directed toward the metal path may be covered by a plate 34 to protect the insert from splash.

When refining is to be carried out the oxygen nozzle inserts 28 and the angular setting of the oxygen nozzle blocks will be selected to give, for the particular molten stream flow rate, the necessary momentum to that oxygen flow required to refine the molten stream so that the molten stream is shattered and an included prism angle is obtained suited to the vessel which is to receive the refined molten material. Thus, for a given molten stream a higher oxygen flow rate is required to remove carbon and silicon together than to remove silicon alone and, therefore, the velocity of the oxygen to achieve the momentum to break up that molten stream will be less, for a given angle of intersection, than that required for the lower oxygen flow rate.

For lower metal flow rates a cylindrical metal stream can be adequately shattered by the oxygen required for refining purposes. To deal with a cylindrical flow a plurality of nozzle blocks 35 may be mounted round the flow path at less than spacing as diagrammatically shown in FIGS. 5 and 6.

The device shown in those Figures comprises a support ring 36 defining eight recesses 37. Each is intended as a guideway for a carriage 38, only four being shown, to support its carriage for radial movement relative to a metal flow path extending coaxially through the ring. Each carriage pivotally supports a nozzle body 39 which will have an individual connection to a gas supply. The choice of number of nozzles will depend upon the circumstances, but with four or eight mounted equispaced, jets of gas will converge at a selected angle from a selected distance on to the metal flow. The ring may be hollow as shown for cooling purposes.

A flux discharge device 40 is mounted above the gas discharge nozzles, as shown in FIG. 1, to provide a curtain of flux falling between the metal stream and each gas nozzle. In the case of a wide thin stream a pair of curtains is provided while in the case of a cylindrical or like stream an annular flux manifold may dispense through an annular outlet a continuous curtain of flux surrounding the stream.

Operation of the refining process will be understood more fully by reference to copending applications Ser. Nos. 640,121 and 640,122, filed May 22, 1967, by Malvern John Rhydderch, having an assignee common to the present application.

What is claimed is:

1. The method of operating spray treatment apparatus comprising gas discharge means for projecting against a freely falling stream of molten metal at least one jet of gas capable of reacting with said molten metal, which method comprises the steps of causing said gas to flow at a rate such as to effect the desired treatment of said molten metal, and adjusting the distance between said gas discharge means and the zone at which said at least one jet impinges on said stream to produce a gas velocity at impingement which will provide a predetermined degree of shatter.

2. The method claimed in claim 1 in which said molten metal falls vertically and in which said distance is adjusted by angularly adjusting said gas discharge means in a vertical plane.

3. The method claimed in claim 2 in which said distance is adjusted by moving said gas discharge means toward and away from said metal stream.

4. The method of maintaining substantially constant a predetermined degree of shatter of a stream of molten metal produced in spray treatment apparatus having gas discharge means for projecting against a freely falling stream of said metal at least one jet of gas capable of reacting with said molten metal, which method comprises the steps of adjusting the velocity of flow of said gas from said gas discharge means to the velocity required to supply the volume needed to treat the metal, and adjusting the distance between said gas discharge means and the zone at which said at least one jet impinges on said stream to produce a gas velocity at impingement which will provide said predetermined degree of shatter.

5. The method claimed in claim 4 in which said molten metal falls vertically and in which-said distance is adjusted by angularly adjusting said gas discharge means in a vertical plane.

6. The method claimed in claim 4 in which said distance is adjusted by moving said gas discharge means toward and away from said metal stream.

7. The method claimed in claim 4 in which said molten metal is an impurity-containing iron, and said gas has a refining effect on said iron. 

2. The method claimed in claim 1 in which said molten metal falls vertically and in which said distance is adjusted by angularly adjusting said gas discharge means in a vertical plane.
 3. The method claimed in claim 2 in which said distance is adjusted by moving said gas discharge means toward and away from said metal stream.
 4. The method of maintaining substantially constant a predetermined degree of shatter of a stream of molten metal produced in spray treatment apparatus having gas discharge means for projecting against a freely falling stream of said metal at least one jet of gas capable of reacting with said molten metal, which method comprises the steps of adjusting the velocity of flow of said gas from said gas discharge means to the velocity required to supply the volume needed to treat the metal, and adjusting the distance between said gas discharge means and the zone at which said at least one jet impinges on said stream to produce a gas velocity at impingement which will provide said predetermined degree of shatter.
 5. The method claimed in claim 4 in which said molten metal falls vertically and in which said distance is adjusted by angularly adjusting said gas discharge means in a vertical plane.
 6. The method claimed in claim 4 in which said distance is adjusted by moving said gas discharge means toward and away from said metal stream.
 7. The method claimed in claim 4 in which said molten metal is an impurity-containing iron, and said gas has a refining effect on said iron. 